FIG. 5 is a partial cross-section of known torque converter 300 with turbine clutch 302. Torque converter 300 includes cover 304 arranged to receive torque, impeller 306, turbine 308, and stator 310. Impeller 306 includes impeller shell 312 with portion 312A having surface 314, and blades 316 fixedly connected to shell 312, for example by brazing. Turbine 308 includes turbine shell 318 with radially outermost portion 318A having surface 320, and blades 322 fixedly connected to shell 318, for example by brazing. Stator 310 includes blades 324 and one-way clutch 325. Clutch 302 includes friction material 326 bonded with adhesive to either surface 314 or 320. Clutch 302 acts as a lock-up clutch for converter 300. For example, pressure in chamber 328 forces shell 318 in axial direction AD to bring friction material 326 into contact with surfaces 314 and 320 to non-rotatably connect shells 312 and 318. Thus, torque transmitted to shell 312 is directly transmitted to shell 318.
In order to bond the friction material to surface 314 or 320, surface 314 or 320 are roughened to facilitate the bonding of the adhesive to surface 314 or 320. Typically, blades 316 and 322 are fixed to shells 312 and 318, respectively, by a brazing process which involves heating the blades and shells. The heating causes some distortion of surfaces 314 and 320. Surfaces 314 and 320 are then machined to remove the distortion. Because of the machining step, the roughening cannot be conducted until after the brazing process. That is, the machining would obliterate the roughening if the roughening is performed prior to the brazing operations.
It is known to use sandblasting, for example with aluminum oxide particles, to roughen surfaces such as surfaces 314 and 320. Following sandblasting, the sandblasted parts must be washed to remove particles remaining after the sandblasting process. However, the respective combinations of shell 312 and blades 316 and shell 318 with blades 322 creates a myriad of nooks, crannies, pockets, and other configurations in which particles can lodge. It is very difficult, it not virtually impossible, to remove the particles by washing or any other means. Particles remaining in the turbine or impeller can adversely affect operation of torque converter 300 or other equipment connected to the torque converter, for example, a transmission pump providing fluid to the torque converter.